Thanks for input.I got the expected result. You have helped me many times. Thank you very much.
– L.TJan 12 '14 at 16:22

I do this just for learning how to use this.unblock() and get the different effects
– L.TJan 12 '14 at 16:27

Akshat is right, fs.readFileSync blocks the whole event loop, it means everything will stop in your server code until the 4M file is read or written. You definitely don't want it to happen in your web-app server.
– imslavkoJan 12 '14 at 19:35